1. Field of the Invention
The present invention relates to an apparatus for testing defects of a sheet-shaped product having an optical film, an apparatus for processing the test data thereof, an apparatus for cutting the same, and a production system thereof. More particularly, in the event of testing the defects of a sheet-shaped product having at least an optical film which is a member of an optical displaying apparatus, the present invention relates to detecting the defects of a monolayer body and/or a laminate body constituting the sheet-shaped product in a state in which a protective layer on a surface of the sheet-shaped product is not disposed, and using the defect information for producing the sheet-shaped product provided in separate sheets.
2. Description of the Related Art
Conventionally, in a maker for producing an optical film, a band-shaped sheet-shaped product having an optical film member is produced by collecting and winding it in a roll form or on a different production line for each step. As this “band-shaped sheet-shaped product”, there are, for example, a polarizing plate source, a retardation plate source, and a laminate film source of a polarizing plate and a retardation plate used in a liquid crystal display device.
An adhesive agent is used for bonding this sheet-shaped product with an optical displaying unit. This adhesive agent is formed in advance as an adhesive layer on the sheet-shaped product, and further a release film (which may also be referred to as a separator) is formed for protection of the adhesive layer.
A sheet-shaped product having a polarizing plate with a laminate structure of FIG. 12 will be shown, and a conventional example of the steps for producing this sheet-shaped product will be described below. First, as preliminary steps, there are (A) a step of obtaining a polarizer, where the polarizer is obtained by drying a polyvinyl alcohol (PVA) film subjected to a dyeing/crosslinking and stretching process, (B) a step of producing a polarizing plate, where the polarizing plate is produced by bonding a triacetylcellulose (TAC) film via an adhesive agent on both surfaces of the polarizer and laminating a polarizer protective layer; here, in the drawings, an antiglare process is performed in advance on the TAC film to be laminated thereon, (C) a step of bonding a separator and a protective film, where the separator is bonded via a strong adhesive agent on one surface of the polarizing plate (lower side in the drawings) and the protective film is bonded via a weak adhesive agent on the other surface (upper side in the drawings). Here, the strong adhesive agent is applied in advance on the separator, and the weak adhesive agent is applied in advance on the protective film. The strong adhesive agent applied on the separator is transferred to the TAC after releasing the separator. The weak adhesive agent applied on the protective film remains as it is formed on the protective film after releasing the protective film, so that substantially the weak adhesive agent is not transferred to the TAC. Through the above-described preliminary steps, a band-shaped sheet-shaped product is produced, collected and wound in a roll form, and subjected to subsequent processes.
In these preliminary steps (A, B, C), a predetermined test is carried out for each step by a testing person. For example, in the case of the step (A), during the transportation of the PVA source, the testing person confirms the defects (foreign substances, stain, twist, surface-adhering substances, and the like) by eye inspection at the timings of the start and the end of winding of the roll. Also, in the case of the step (B), in collecting and winding the obtained polarizing plate source in a roll form, the testing person confirms the defects (foreign substances, stains, knicks, twists, creases, and the like) by eye inspection. Also, the polarizing plate source after bonding is automatically tested by a defect testing apparatus (a known apparatus for capturing images of foreign substances, stain, and the like with a camera, and determining the defects by image processing); the defects are confirmed by a monitor; and the test was mainly used for state management (supervision) by monitoring the defects.
Also, in the case of the step (C), in collecting and winding the obtained band-shaped sheet-shaped product source in a roll form, the testing person confirms the defects (foreign substances, stain, twist, surface-adhering substances, and the like) by eye inspection at the timings of the start and the end of winding of the roll, and performed the ranking (good, bad, permissibility of shipping) of the sheet-shaped product source by evaluating these defects.
Subsequently, as the posterior steps, there is (D) a step of testing the source roll. Here, the appearance of the sheet-shaped product roll is tested by a roll-form automatic source testing apparatus and/or by eye inspection of a testing person. The roll-form automatic source testing apparatus is a known apparatus that captures images of poor winding, poor appearance, and the like with a camera, and performs image processing to determine the defects. Also, there is (E) a step of cutting into a sheet-shaped product provided in separate sheets. Here, a sheet-shaped product is drawn out from the source roll, and is cut to have a predetermined size. As the cutting method, there are, for example, constant-measure cutting, continuous punching-out, and the like. Also, there is (F) a step of testing the sheet-shaped product provided in separate sheets. Here, testing by a sheet-form automatic testing apparatus and by eye inspection of a testing person are carried out. The sheet-form automatic testing apparatus is an apparatus that automatically tests the defects of the sheet-shaped product provided in separate sheets, where light is radiated; images of the reflected light thereof or images of transmitted light thereof are captured with an imaging section such as a line sensor or a two-dimensional TV camera; and the defects are detected on the basis of the captured image data. Also, the image data are captured in a state in which a polarizing filter for testing intervenes in the optical path between the light source and the imaging section. Typically, the polarization axis (for example, the polarization absorption axis) of this polarizing filter for testing is disposed to be in a state (crossed nicol form) perpendicular to the polarization axis (for example, the polarization absorption axis) of the polarizing plate which is an object of testing. By disposing it in crossed nicol, an image of total black is input from the imaging section if there are no defects; however, when there are defects, that part will not be black and will be detected as bright points. Therefore, the defects can be detected by setting a suitable threshold value.
As described above, in the posterior steps (D, E, F), the sheet-shaped product source wound in a roll form is drawn out and is cut into a sheet-shaped product provided in separate sheets of a predetermined size, followed by a predetermined defect testing to determine the quality for shipping.
In the above-described whole production steps, the defect testing of individual sheet-shaped products are carried out after being cut into a sheet-shaped product provided in separate sheets. Therefore, the product is determined to have a poor quality, for example, if one defect is present in the sheet-shaped product, thereby raising a problem in that the yield of the final sheet-shaped product provided in separate sheets obtained from the source roll will be poor.
Also, in the case of testing a sheet-shaped product provided in separate sheets, the product is in a state in which a separator or a protective film is bonded on the sheet surface. When the sheet-shaped product provided in separate sheets is tested in this state, because the separator and the protective film have a birefringence property (retardation), the linearly polarized light will be elliptically polarized light in such a case, so that substantially the polarizing plate and the polarization filter for testing will not be in a state of crossed nicol. As a result, this raises a problem in that the testing of the defects of the polarizing plate included in the sheet-shaped product cannot be performed with a good precision.
Here, as an apparatus for testing defects of a laminate film that solves the aforementioned problem, a polarizing plate testing apparatus disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2005-9919 is known in the art. This polarizing plate testing apparatus includes a light source and a polarization filter for testing that converts the light from this light source into linearly polarized light, where this linearly polarized light is input into a polarizing plate having a protective film (corresponding to a retardation layer), and the defects are detected on the basis of transmitted light images thereof. Further, on the optical path on which the light from the light source is transmitted through the polarizing plate having a protective film, a retardation plate that compensates for the birefringence of the light caused by the protective film is disposed. By separately disposing this retardation plate, the phase change caused by the protective film is cancelled, so as to compensate for the birefringence of the light caused by the protective film. Further, in order to compensate for the birefringence caused by the protective film that differs slightly product by product, there is disclosed a construction example in which an optical element for variable polarized light that can adjust the phase angle of light with use of voltage is disposed.
However, in the above-described JP-A No. 2005-9919, there is a need to dispose the retardation plate for testing or the optical element for variable polarized light separately, leading to additional increase in the number of components and also inviting decrease in the quantity of light of the light source due to the presence of additional intervening components. This lowers the precision of testing, so that there may be cases that cannot withstand the demand for testing of high precision and high product quality that are required in the polarizing plates of recent years.
Also, in order to increase the precision of testing the defects, testing by eye inspection of a person is carried out; however, since this is an eye inspection, it is necessary to take a long period of time for the testing. For this reason, the productivity is poor and a large number of testing persons are needed, thereby raising a problem of leading to increase in the production costs.
Further, in the testing after being cut into separate sheets, determination of being good or bad is carried out using a uniform threshold value (the severest value) as a condition. However, depending on the user (for example, a liquid crystal apparatus assembling manufacturer), the determination of being good or bad of the degree of the defects may differ. There is a case such that, even if one product is bad for a certain manufacturer, the product may have an excessive quality for another manufacturer. Then, there is a demand from the manufacturer side for carrying out testing that meets the quality requirement of each manufacturer and for cost reduction and shortening of the deadline of receiving the products. Due to such demands, an improvement in the testing steps has been strongly desired.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a defect testing apparatus for testing the defects of a sheet-shaped product having at least an optical film which is a member of an optical displaying apparatus that can improve the yield, reduce the production costs, and greatly improve the productivity by using a determination condition that differs user by user, as well as a test data processing apparatus thereof, a cutting apparatus thereof, a production system thereof, and a test data processing method.